Improved Electrical Properties of AlGaN/GaN MIS-HEMTs with Thermal and Plasma-enhanced ALD Al2O3 Gate Dielectric

Abstract In this paper, AlGaN/GaN high-electron-mobility transistors (HEMTs) and metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) with 5 nm Al2O3 gate dielectric grown by thermal atomic layer deposition (TALD) and plasma-enhanced atomic layer deposition (PEALD) were investigated. Polarization Coulomb field (PCF) scattering intensity was reduced and electron mobility was improved due to low additional polarization charges and a high two-dimensional electron gas density (n2d) in MIS-HEMTs. PEALD MIS-HEMT has a lower threshold voltage (Vth) and more significant gate leakage current (IG) suppression than TALD MIS-HEMT. Compared with HEMT, a lower IG (~ 4 orders), a higher on/off current ratio (Ion/Ioff) (~ 4 orders), a higher transconductance peak (gm.peak) (~ 26%) are recorded in PEALD MIS-HEMT. Moreover, breakdown voltage (VBR) of PEALD MIS-HEMT and TALD MIS-HEMT is improved by ~ 53% and ~ 33% respectively, due to the effective suppression of electric field at gate edge.